Intermediate
Theory of Computation
Q75 / 100
Why is left recursion a problem for top-down (LL) parsers, and how is it resolved?
Correct! Well done.
Incorrect.
The correct answer is B) A left-recursive rule like A → Aα | β causes infinite recursive descent without consuming input; it is eliminated by rewriting the grammar as A → βA' and A' → αA' | ε
B
Correct Answer
A left-recursive rule like A → Aα | β causes infinite recursive descent without consuming input; it is eliminated by rewriting the grammar as A → βA' and A' → αA' | ε
Explanation
A predictive parser expanding A → Aα would call itself again before reading input, looping forever. The standard fix rewrites left recursion into right recursion using a fresh non-terminal, preserving the language while making top-down parsing feasible.
Progress
75/100